Background and objectives: Diabetes mellitus (DM) is a common endocrinopathy in dogs, but only few studies described laboratory changes in diabetic dogs and current knowledge is mainly derived from textbooks. In addition, information on epidemiology and management in general practice is limited, and no current data concerning diabetic dogs in Germany can be found in the literature. The aim of this study was therefore to evaluate retrospectively laboratory changes and epidemiological data based on laboratory submissions to a large commercial veterinary laboratory, as well as prospectively collect information on management and treatment of DM in Germany. Such information might guide future recommendations concerning management of canine DM in Germany. Material and methods: The basis of the retrospective examination was the dataset of 145072 records from 2015 to 2018, provided by the commercial veterinary laboratory SYNLAB Vet. Fructosamine was used to distinguish diabetic (≥ 370 µmol/l) from non-diabetic dogs as well as to differentiate between good (370 – 450 µmol/l) and bad ( 450 µmol/l) glycaemic control of diabetic dogs. Besides the evaluation of epidemiological data (prevalence, age, gender and neutering status) and selected laboratory geriatric profile data (haematology, clinical chemistry, total thyroxine) were compared between groups. Non-parametric tests and effect size measures were used to examine the relevance of the identified differences. In the prospective part of this investigation between April 2021 and December 2022, DGGR lipase and vitamin B12 concentrations of 54 diabetic dogs in Germany were evaluated in addition to the selected laboratory parameters of the geriatric profile. Data on signalment, age at DM diagnosis, current and former nutritional status and seasonality of DM diagnosis as well as medical management (insulin type and dose, diet and feeding practices, quality of diabetic control, concomitant diseases and complications) were obtained from questionnaires submitted alongside blood samples.   Results: The prevalence of canine DM was 5.12 % (confidence interval 5.01 – 5.24 %). Median age of diabetic dogs was 9 (interquartile range 6 – 12) years in the retrospective population and 10 (8 – 12) years at the time of study participation in the prospective cohort (median age at DM diagnosis was 9 [7.8 – 10.7] years). In the retrospective part, male intact and female intact dogs were significantly (p 450 µmol/l). Diabetic diets were only offered to 58 % (31/53) of dogs, and most diabetic dogs received food twice daily (44/53; 83 %). Fructosamin was most frequently (27/49; 55 %) used to make insulin dose adjustments, and in 49 % (24/49) of dogs, more than one glycaemic parameter (including clinical signs) was used. For those diabetic dogs with poor glycaemic control, this assessment was usually made based on more than one parameter (30/38; 79 %), with polyuria/polydipsia being the most common criterion (25/38; 66 %). Complications of DM were present in 50 % (27/54) of diabetic dogs and diabetic cataract was the most frequent (18/54; 33 %). Concomitant diseases (29/54; 54 %), especially pancreatitis (14/54; 26 %), were common, too. Gastrointestinal symptoms (excluding weight loss) were present in 10/54 (19 %) dogs. In the retrospective study, the most relevant laboratory finding was an increase in alkaline phosphatase (AP) (p 213 U/l was present in 24.5 % (13/53) and low cobalamin weiterlesen